Conventional armor such as for protecting vehicles is subjected to a variety of projectiles designed to defeat the armor by either penetrating the armor with a solid or jet-like object or by inducing shock waves in the armor that are reflected in a manner to cause spalling of the armor such that an opening is formed and the penetrator (usually stuck to a portion of the armor) passes through, or an inner layer of the armor spalls and is projected at high velocity without physical penetration of the armor.
Some anti-armor weapons are propelled to the outer surface of the armor where a shaped charge is exploded to form a generally linear “jet” of metal that will penetrate solid armor; these are often called Hollow Charge (HC) weapons. A second type of anti-armor weapon uses a linear, heavy metal penetrator projected at high velocity to penetrate the armor. This type of weapon is referred to as EFP (explosive formed projectile), or SFF (self forming fragment), or a “pie charge,” or sometimes a “plate charge.”
In some of these weapons the warhead behaves as a hybrid of the HC and the EFP and produces a series of metal penetrators projected in line towards the target. Such a weapon will be referred to herein as a Hybrid warhead. Hybrid warheads behave according to how much “jetting” or HC effect it has and how much of a single big penetrator-like an EFP it produces.
Various projection systems are effective at defeating HC jets. Among different systems the best known are reactive armors that use explosives in the protection layers that detonate on being hit to break up most of the HC jet before it penetrates the target. The problem is that these explosive systems are poor at defeating EFP or Hybrid systems.
Another type of anti-armor weapon propels a relatively large, heavy, generally ball-shaped solid projectile (or a series of multiple projectiles) at high velocity. When the ball-shaped metal projectile(s) hits the armor the impact indices shock waves that reflect in a manner such that a plug-like portion of the armor is sheared from the surrounding material and is projected along the path of the metal projectile(s), with the metal projectile(s) attached thereto. Such an occurrence can, obviously, have very significant detrimental effects on the systems and personnel within a vehicle having its armor defeated in such a manner.
While the HC type weapons involve design features and materials that dictate they be manufactured by an entity having technical expertise, the later type of weapons (EFP and Hybrid) can be constructed from materials readily available in a combat area. For that reason, and the fact such weapons are effective, has proved troublesome to vehicles using conventional armor.
The penetration performance for the three mentioned types of warheads is normally described as the ability to penetrate a solid amount of RHA (Rolled Homogeneous Armor) steel armor. Performances typical for the weapon types are: HC warheads may penetrate 1 to 3 ft thickness of RHA, EFP warheads may penetrate 1 to 6 inches of RHA, and Hybrids warheads may penetrate 2 to 12 inches thick RHA. These estimates are based on the warheads weighing less than 15 lbs and fired at their best respective optimum stand off distances. The diameter of the holes made through the first inch of RHA would be; HC up to an inch diameter hole, EFP up to a 9 inch diameter hole, and Hybrids somewhere in between. The best respective optimum stand off distances for the different charges are: standoff distances for an HC charge is good under 3 feet but at 10 ft or more it is very poor; for an EFP charge a stand off distance up to 30 feet produces almost the same (good) penetration and will only fall off significantly at very large distances like 50 yards; and for Hybrid charges penetration is good at standoff distances up to 10 ft but after 20 feet penetration starts falling off significantly. The way these charges are used are determined by these stand off distances and the manner in which their effectiveness is optimized (e.g., the angles of the trajectory of the penetrator to the armor). These factors effect the design of the protection armor.
Conventional armor is subjected to a variety of projectiles designed to defeat the armor by penetrating the armor. Some anti-armor weapons are propelled to the outer surface of the armor where a shaped charge is exploded to form a generally linear “jet” of metal that will penetrate solid armor. Such weapons are often called Hollow Charge (HC) weapons. A rocket propelled grenade (“RPG”) is such a weapon. An RPG 7 is a Russian origin weapon that produces a penetrating metal jet, the tip of which hits the target at about 8000 m/s. When encountering jets at such velocities solid metal armors behave more like liquids than solids. Irrespective of their strength, they are displaced radially and the jet penetrates the armor.
Various protection systems are effective at defeating HC jets. Among different systems the best known are reactive armors that use explosives in the projection layers that detonate on being hit to break up most of the HC jet before it penetrates the target. Also known are “bulging armor” components which upon impact by the jet, distort into the jet path to deflect or break up the jet to some extent. Both such systems are often augmented by what is termed “slat armor,” a plurality of metal slats or bars disposed outside the body of the vehicle to prevent the firing circuit for an RPG from functioning.
Also, as recently disclosed by the Foster-Miller company as part of its RPG Net™ Defense Systems, a net suspended alongside and spaced from the surface of an armored vehicle can act to disrupt RPGs by breaking and/or defeating the RPGs. These nets are reported to be able to crush the foreword conical surface of the RPG 7 to render the fuze inoperative and thereby prevent detonation and shaped charge formation in a significant percentage of RPG 7 impacts.
While any anti-armor projectile can be defeated by metal armor of sufficient strength and thickness, extra metal armor thickness is heavy and expensive, adds weight to any armored vehicle using it which, in turn, places greater strain on the vehicle engine, and drive train.
Armor solutions that offer a weight advantage against these types of weapons can be measured in how much weight of RHA it saves when compared with the RHA needed to stop a particular weapon penetrating. This advantage can be calculated as a protection ratio, the ratio being equal to the weight of RHA required to stop the weapon penetrating, divided by the weight of the proposed armor system that will stop the same weapon. Such weights are calculated per unit frontal area presented in the direction of the anticipated trajectory of the weapon.
Thus, there exists a need for an armor system that can defeat projectiles and jets from anti-armor devices, particularly rocket propelled grenades, without requiring an excess thickness of metal armor. Preferably, such an armor system would be made of materials that can be readily fabricated and incorporated into a vehicle design at a reasonable cost, and even more preferably, can be added to existing vehicles.
As the threats against armored vehicles increase and become more diverse, combinations of armor systems are needed to defeat the various threats. An armor system that raises the protection level of an armored vehicle to include HC charges, both missile-borne and stationary, is described.